What was el nino

Every few years, those prevailing Pacific trade winds that blow east to west can weaken. Scientists are still debating the nuances of exactly why this happens. When the trade winds weaken, all that warm water that was piled up near Indonesia starts sloshing back eastward, pulled back down by gravity. What's more, the underwater layer known as the thermocline starts sinking.

As a result, there's less cold water rising up from the deep ocean near South America — so the waters near Peru start warming up. Here's another diagram:. This causes sea surface temperatures in the east and central Pacific to start rising and the trade winds to weaken even further.

What's more, rainfall starts following that warm pool of water as it travels eastward. The rain is essentially moving east. It can also cause the jet stream to start stretching from the Eastern Pacific across the southern United States, bringing rainfall and storms with it. More on that below. And, importantly, atmospheric conditions were responding in turn, with more rain over the central Pacific and less rain over Indonesia:.

Sea surface temperature departures from average based on — at the end of February And stronger. Notice how the anomalous warm area has moved east and is much, much warmer than usual:. Some forecasters have even dubbed this one a potential "Godzilla. A paucity of rainfall in Indonesia this fall allowed manmade forest and peat fires to rage out of control , choking the region in a thick toxic haze. On the flip side, however, the event has also fostered more wind shear in the Atlantic that has curtailed hurricane activity there.

But even here, nothing is certain. See here for a lucid explanation by Columbia University's Anthony Barnston. This is an intricate chain of events, and small kinks at certain points can affect the ultimate outcome.

As such, Becker cautions people to think not in terms of certainties but in terms of probabilities. Official outlooks from the Climate Prediction Center are available here.

What's more, even if rain does come, that may not be enough to completely erase the massive water deficit that California has built up over the past five years. The state likely needs record precipitation to end the drought, and it also needs the right mix of rain to recharge the reservoirs and snow in the Sierra Nevada mountains to melt during the spring and summer.

Also, be warned: Heavy rain after a drought can bring floods and mudslides. Southern California got a possible preview in mid-October, when a short burst of intense rains led to major mudflows that trapped hundreds of cars. So people need to be ready. The reasons varied: drought and reduced crop yields in Australia and India, forest fires in Indonesia, less productive fisheries in Peru.

So think of this table as more a rough guide than gospel. There are also two important twists here. Animals This frog mysteriously re-evolved a full set of teeth. Animals Wild Cities Wild parakeets have taken a liking to London.

Animals Wild Cities Morocco has 3 million stray dogs. Meet the people trying to help. Environment COP26 nears conclusion with mixed signals and frustration. Environment Planet Possible India bets its energy future on solar—in ways both small and big. Environment As the EU targets emissions cuts, this country has a coal problem.

Paid Content How Hong Kong protects its sea sanctuaries. History Magazine These 3,year-old giants watched over the cemeteries of Sardinia. Science Coronavirus Coverage What families can do now that kids are getting the vaccine.

Magazine How one image captures 21 hours of a volcanic eruption. Science Why it's so hard to treat pain in infants. Science The controversial sale of 'Big John,' the world's largest Triceratops. Science Coronavirus Coverage How antivirals may change the course of the pandemic. Travel A road trip in Burgundy reveals far more than fine wine.

Travel My Hometown In L. Subscriber Exclusive Content. Warm water is pushed back east, toward the west coast of the Americas. South American fishermen first noticed periods of unusually warm water in the Pacific Ocean in the s. The warmer waters cause the Pacific jet stream to move south of its neutral position.

With this shift, areas in the northern U. But in the U. Gulf Coast and Southeast, these periods are wetter than usual and have increased flooding. During winter, this leads to wetter conditions than usual in the Southern U.